The invention relates to hitches for towing.
Hitches allow vehicles to be attached together for towing, and typically are configured as balls or as pintle hooks. Ball hitches are typically used for lighter loads, e.g. cargo trailers, recreational trailers, etc., while pintle hooks are employed for heavier loads, e.g. portable compressors and construction equipment. Ball hitches come in a variety of standard sizes, dictated by the load to be towed, e.g. a two inch diameter ball typically has a load rating of 5,000 pounds, while a 2 5/16 inch diameter ball has a load rating of 7,000 pounds, and the ball used must correspond to the coupler size on the trailer tongue. Typically the balls are formed on a threaded pin and are removably bolted through a provided hole in the hitch support. The balls are thus easily changed but their construction provides lower ratings because of the susceptibility of threaded pins to shearing, etc., especially due to the diameter restriction on the pin needed to permit the presentation of a spherical undersurface of the ball to the coupler. Pintle hooks have much higher load rating, e.g. 14,000 pounds and higher, depending upon size. Pintle hooks are adapted to receive a lunette, i.e. an annular eye ring at the end of the trailer tongue, through which the hook extends, and typically include a latch for securing the lunette on the pintle hook during towing.
There are numerous situations where trailers have a variety of coupling configurations, e.g. in construction, rental yards, utilities, repair and sales facilities, etc. As has long been recognized it would be desirable to have a reliable, strong, multi-purpose hitch that is easily employed and withstands the rugged environmental conditions to which hitches are normally exposed. Prior suggestions for multiple hitch arrangements have usually required sacrifice of strength, durability or safety with one type of attachment in order to achieve the capability of another type of attachment. Most have also involved serious limitation, still, in the range of attachments that are made possible.
For example, Charlton U.S. Pat. No. 3,779,653 and Thelen U.S. Pat. No. 3,963,266 provide pintle hooks with only a single size ball formed at the hook ends. Use of interchangeable balls, for example with threaded pins, would only provide a load rating approximately that of a standard ball hitch, not acceptable for hauling typical lunette coupled trailers. Furthermore Chandler's and Thelen's constructions are susceptible to damage under a number of circumstances. Osborn U.S. Pat. No. 2,827,307, Riddle U.S. Pat. No. 2,911,233, Dees U.S. Pat. No. 3,801,134 and Christansen U.S. Pat. No. 4,029,333 provide hitches with selectable positions; while Rathsack U.S. Pat. No. 3,837,674 and Koch U.S. Pat. No. 4,379,569 provide converters for attaching other hitch configurations to a pintle hook.